In an optical element driving device, an optical element such as a lens and a diaphragm is moved in a predetermined direction by a driving force of a drive motor. The optical element driving device is provided in, for example, a disk drive device having an optical pickup, an imaging device such as a still camera and video camera, or a camera module incorporated in a mobile terminal.
For example, the disk drive device performs recording or reproduction of an information signal on a disk-shaped recording medium such as an optical disk and a magneto-optical disk. Upon the recording and reproduction of an information signal, the optical pickup is moved in the radial direction of the disk-shaped recording medium. The optical pickup includes a moving base guided and moved by, for example, a guide shaft in the radial direction of the disk-shaped recording medium and an objective lens driving device arranged on the moving base, and the irradiation light traveling through the objective lens is focused on a recording surface of the disk-shaped recording medium.
Examples of the optical element driving device provided in the disk drive device include a device that is moved by a lead screw used to allow a given lens arranged in the optical pickup to rotate by a driving force of a drive motor (e.g., refer to Patent Literature 1).
In the optical element driving device disclosed in Patent Literature 1, a nut is threadably engaged with a lead screw, and a lens holder which holds a lens and is formed integrally with the nut is moved in the axial direction of the lead screw by feeding the nut with the rotation of the lead screw. The lead screw has one end portion that is connected to a drive unit of the drive motor and the other end portion that is placed and rotatably supported on a thrust bearing.
In the optical element driving device using such a lead screw, the nut may be excessively moved and even in contact with the thrust bearing due to defects in control software or a detector, and a reaction force to the opposite side of the thrust bearing is applied to the lead screw and the drive unit. Thus, a portion of the drive unit is pressed against the inner surface of a casing of the drive motor during rotation and the rotation of the drive motor may be disabled, which is called stuck.
Thus, in the optical element driving device disclosed in Patent Literature 1, a nut idling portion is formed on both end portions in the axial direction of the lead screw to allow idle rotation of the nut. In addition, a nut return spring is provided to allow the nut to be threadably engaged with a threaded engagement portion of the lead screw, thereby preventing the occurrence of stuck. Thus, when the nut is fed to the end portion in the axial direction of the lead screw, the nut is idling with the lead screw by the nut idling portion, thereby preventing the occurrence of stuck. In addition, the nut is biased toward the threaded engagement portion by the nut return spring, and when the lead screw rotates in the opposite direction after the idling of the nut, the nut is threadably engaged with the threaded engagement portion and the thread engagement is restored to a normal condition.